The evaporator temperature sensor can fail, causing the AC compressor not to cycle. If the AC compressor does not turn on, the AC system will not blow cold air. If the compressor is stuck on, the air will be very cold at first, before warming up.

After taking it to a shop they replaced a variety of pressure switches and other components, only to have the system fail two days later. I took it to a different mechanic and they quickly diagnosed the issue as a faulty temperature sensor - a relatively inexpensive fix.

I used the self diagnostic feature for the A/C system's lack of producing cold air. It read to have a slight overage of BAR pressure (2.7 witch is 0.3 over the specified limit), yet the compressor clutch remained engaged the entire time during my 2 minute visual observation . The lines felt as if the difference between the hot and cold side (supply and return lines) wasn't far enough away from each other to produce a noticeable difference inside the cabin (temperature wise). I pushed the low side valve open to release some of the pressure down so that the BAR was within factory specs and now the compressor clutch no longer engages. I am going to change out the cabin air filter next but now see from the known issues submitted leads me to believe the evap. sensor is to blame.

I have a 2005 Mercedes C230 Kompressor Sport 4 door sedan. My AC was not working so I changed my compressor and flushed out the ac system and recharged it. The ac would blow cold for 2 to 3 minutes then start blowing hot air. My temp setting dial was set to the coldest when this happened. My mechanic was stumped. After reseraching on the internet, I concluded it was the AC Rerigerant Evaporator Temperature Sensor (part number 220 830 0772) which I got from my local Mercedes "Stealership". My mechanic is working on putting in the sensor now. I live in Southern California so summers are hot and dry. I need my AC to blow cold. I will keep you all updated.